This invention relates to a press contact type connector for a flat electrical cable.
One type of flat cable has heretofore been known which has parallel inner conductors and an insulator thereover and has on the outer surface thereof an electrically conductive or semi-conductive layer (hereinafter referred to as a "conductive layer") made of a metal foil or an electrically conductive plastic material, for either shielding purposes or in order to allow the conductive layer to serve as a common electrode. One type of conventional connector employed for connection of such cable has heretofore been arranged such that press contact type contact terminals, each having a bifurcated distal end portion, are inserted into the insulator in a flat cable in such a manner that the bifurcated distal end portion of each contact terminal straddles the corresponding conductor in the cable so as to be in electrical contact with the conductor.
In use of such a connector, because the conductive layer provided on, for example, the surface of the flat cable, is disposed in close proximity to the conductors inside the cable, it is necessary to prevent contact between the conductive layer and the contact terminals brought into contact with the conductors in the cable, and, for this purpose, it has heretofore been a general practice to partially remove the above-described conductive layer provided on the surface of the insulator before the bifurcated distal end portions of the contact terminals are inserted into the insulator.
However, because such shielding layer, e.g., a conductive layer, needs to be securely adhered onto the insulator so that it is not separated during use of the cable, it is a time-consuming operation to partially remove the shielding layer when connecting a conventional connector to the cable, and this disadvantageously leads to an increase in costs and also involves a lowering in electrical characteristics of the cable due to the removal of a part of the shielding layer.
In order to allow a connector to be connected to a shielded flat cable without the need to remove a part of the shielding layer such as a conductive layer which is provided on a terminal portion of the cable, it may be thought to increase the thickness of the insulator in the cable on the side thereof which is adjacent the shielding layer and insert the contact terminals of the connectors into the cable from the side thereof which is remote from the shielding layer. In such case, however, various problems are created. For example, the flexibility of the cable is decreased, and the cable becomes unsuitable for installation with a high packing density.
As other connecting means, connectors for a flat cable similar to the above have been disclosed in the specifications of Japanese Utility Model Publication Nos. 26518/1984 and 3185/1982. These connectors are arranged such that an insulating coating is applied to either the distal end portion or proximal portion of a bifurcated end portion of each contact terminal of a connector body so that, when the contact terminals are inserted into the insulator in a cable from the side thereof which is remote from the shielding layer, the contact terminals are insulated from the shielding layer but allowed to be in electrical contact with only the corresponding conductors. However, when the contact terminals are partially covered with an insulating coating so that, when the contact terminals contact the shielding layer, the former is prevented from conducting to the latter, it must be certain that an insulating coating is completely applied to each such terminal. In practice, however, it is difficult to completely apply an insulating coating to each such contact terminal, which means that a reduction in adhesion strength of the coating layer at, particularly, the edge portion of the bifurcated distal end of the contact terminal is usually unavoidable. In consequence, a portion of the coating layer which is necessary for insulation may be separated during a connecting operation, resulting in undesirable electrical contact between a contact terminal and the shielding layer on the cable. Therefore, this prior art is not necessarily satisfactory in terms of reliability. In addition, the necessity for an insulator coating operation disadvantageously leads to an increase in the production cost of such a connector.
Furthermore, the conventional press contact type connectors involve the problem that a contact failure may be caused when a tensile load acts on the cable.
It is an object of the present invention to solve the above-described problems of the prior art and provide a connector for a flat cable which is so designed so that the connector can readily be connected to the flat cable without lowering the electrical characteristics of the cable, and the connector can be produced economically.